1. Technical Field
Example aspects described herein relate to medical image processing and, in particular, relate to procedures, systems, apparatuses, and computer program products for interactive pre-operative assessments of hepatic vascular and biliary systems.
2. Description of Related Art
The human liver receives approximately 30% of resting cardiac output. It is a highly vascular organ having three vascular systems: the portal vein, the hepatic vein, and the hepatic artery systems. In addition, it has a biliary system, in which the bile duct delivers bile from the liver and gallbladder into the duodenum.
Surgical intervention on the liver can be challenging because of the complex vascular anatomy of the liver. Generally speaking, after a successful operation a patient will have sufficient remaining liver tissue supplied by all four vessel systems. One way to achieve this is to perform a pre-operative hepatic vascular assessment that includes good segmentation of vessels and bile ducts and establishes reliable, quantitative spatial relationships among the vessel systems.
Good segmentation of vessels, however, can be difficult to achieve. For example, branches of hepatic artery can be very thin—as small as a single pixel wide—making segmentation of these branches difficult. Also, the imaging contrast between a small vessel branch and nearby anatomical structures can be very low. Accordingly, widely-used segmentation techniques like region growing typically do not generate sufficiently satisfactory output. Atlas and model based approaches also may not offer the desired precision because liver vascular anatomies vary largely from one patient to another. Therefore, efficiently and quickly segmenting small vessels and/or vessels having low contrast remains challenging.
Reliably assessing a patient's biliary system also can be difficult to achieve. A pre-surgical assessment of a patient's bile ducts has significant clinical importance because post-surgical bile duct complication is a commonly encountered problem. In a pre-surgery assessment, however, bile ducts often are scanned with different contrast agents and with different modalities than other intrahepatic anatomies, such as the hepatic vascular system. For example, most intrahepatic anatomies may be scanned with magnetic resonance (MR) or computer tomography (CT) techniques, while the biliary system may be scanned by magnetic resonance cholangiopancreatography (MRCP) or CT cholangiography (CTC) techniques. In these instances, the different scans of the various intrahepatic systems must be aligned in order to analyze the patient's bile duct anatomy together with the other intrahepatic anatomies. Accurate alignment requires that scans of the biliary system be well-aligned with scans of the other anatomies. However, in the anatomy of the liver the portal vein and the bile ducts are parallel but not overlapped. Thus, use of conventional registration algorithms that maximize the overlap of two objects by minimizing the spatial difference between the objects may not result in well-aligned scans.
Furthermore, changes in a patient's body posture can cause noticeable distortion of the liver, which is a soft tissue organ. For example, during scans of a patient's biliary system, the shape of a patient's liver may be distorted as compared to its shape during a previous scans of the patient's hepatic vascular system. In this example, alignment of the biliary scans with the vascular scans, while complicated by the spatial offset described above, may be further complicated by the effects of the distortion.
As evident from the discussion above, known methods and systems do not adequately provide an interactive vessel segmentation procedure that efficiently generates 3D vessel segmentation. Known methods and systems also do not adequately allow for pre-operative assessment of the vascular and biliary systems. And known systems do not offer a combination of quantification, flexibility, and ease-of-use desired by physicians.